Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$106.28	12.147%	$119.1898	$119.19	$119.20	$119.20
Purchase #2	$190.33	9.795%	$208.9728	$208.97	$208.95	$209.00
Purchase #3	$246.72	3.153%	$254.4991	$254.50	$254.50	$254.50
Purchase #4	$134.79	6.506%	$143.5594	$143.56	$143.55	$143.60
Purchase #5	$159.89	8.691%	$173.786	$173.79	$173.80	$173.80
Purchase #6	$82.92	7.853%	$89.4317	$89.43	$89.45	$89.40
Purchase #7	$26.96	5.185%	$28.3579	$28.36	$28.35	$28.40
7 purchase totals =	$947.89		$1,017.7967	$1,017.80	$1,017.80	$1,017.90